Flat-spiral power spring



CTI

lPatented May 17, 1927.

UNITE-D STATES PATENT OFFICE.

ALBERT S. HOWELL, OF CHICAGO, ILLINOIS, ASSIGNOR T0 THE BELL 8c HOWELL COM- PANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

FLAT-SPIRAL POWER SPRING.

Application led December My invention has for its general object the provision of' a flat spiral powerspring with a view toward decreasing the variance of power of the spring as it unwinds and increasing the smoothness and uniformity of the operation thereof. ,t

The invention is particularly adapted for spring driven motion picture cameras where smoothness and uniformity of operation throughout a relatively great run of the power spring is important.

With this object in view my invention consists in certain features of novelty in the construction, combination, and arrangement of parts by which the said object and certain other objects, hereinafter appearing, are effected, all as fully described with reference to the accompanying drawing and more particularly pointed out in the appended claims.

In the said drawing- Figure 1 is a side elevation of a spring motor mechanism embodyingr my invention.

Figure 2 is a side elevation of the winding and driving hub of the motor.

Figure 3 is a face view of the inner portion of the power spring of my invention laid out flat.

Like characters of reference indicate like parts in the several views.

Referring to the drawings 1 designates a mechanism frame which carries a centrally disposed revoluble spindle 2 projecting outwardly from one side of the frame and provided with an enlarged hub 3 on the outside of the frame. See Figs. 1 and 2. A flat .spiral power spring 4 encircles said hub 3 and has its inner end secured to said hub, in a manner hereinafter described, and has its outer end secured in a suitable manner to a projectingmstud 5 secured to the frame.

T he spindle 2 is hollow and is provided in its bore with a clutch formation `6 for winding the spring, and the spindle is connected through a one Way driving connection, not shown, with gearing carried by the frame, not shown, for driving the gearing and for permitting Winding of the spring.

The hub 3 of the spindle is provided with flanges 7 at the ends thereof of a height approximately equal to the thickness of the spring 4, and corresponding slots 8 are cut in these flanges in tangential relation `with the periphery of the intermediate portion of the hub. The edges of the spring 4 adjacent 12, 1925. Serial No. 75,008.

its inner end are cut away, as designated at 9, see Fig. 3, forming ears 10 at the extreme inner end of the spring, and the inner end of the spring is secured to the hub by the ears 10 engaging in respective slots 8 with the narrow portion 'of the spring engaged between the flanges T and the normal width portion of the spring adjacent thereto seat? ing on the peripheries of the flanges.

The inner portion of the spring 4 is apertured longitudinally thereof as designated at 11. See Fig. This aperture is disposed centrally of the spring and gradually increases in Width toward the inner end of the spring, and terminates at its inner end in a relatively abrupt and short tapered portion 12. `Thus the apertured portion of the spring gradually decreases in cross sectionr toward the inner end of the spring with corresponding gradual weakening of this portion of the spring; The tapered inner terminal portion 12 of the aperture 11 serves to distribute the flexure of the spring at the inner end of the aperture with obvious advantage.

The aperture 11 is interrupted intermediate its length by a cross tie 13 integral with the spring 4 and connecting the portions of the spring formed by the aperture to maintain the spacing of these portions.

In operation the weakened inner portion of the spring 4 serves to decrease the radial pressure exerted on the outer convolutions of the springr thereby decreasing the friction between tlie convolutions of the spring. In addition the weakened inner portion of the spring decreases the eccentric tendency of.

the spring with obvious advantage particularly where the spring is confined in a casing. As a result a smooth and uniform operation throughout a relatively great run of the spring is obtained.

While I have herein shown and particularly described the preferred embodiment of my invention, I do not Wish to be limited to the precise details of construction shown as changes may readily be made without departing from the spirit of my invention, but having" thus described my invention, I claim as new and desire to secure by Letters Patent the following claims:

1. As an article of manufacture a flat spiral power spring having an inner portion thereof apertured longitudinally thereof, said aperture being disposed centrally of the Inu spring and gradually increasing in width toward the inner end of the spring, the spring having a cross tie integral therewith and disposed intermediate the length of said aperture and connecting the portions of the spring formed by the aperture. i

2. As an article of manufacture.a flat spring power spring having the inner portion thereof apertured longitudinally thereof, said aperture being disposed centrally of the sprlng and gradually increasing in Leashes width toward the inner end of the spring and terminating at its inner end in a rela tively abrupt and short tapered portion, the spring having a cross tie integral therewith intermediate the length of the aperture and connecting the portions thereof formed by said aperture.

In witness whereof I hereunto aflix my signature this 8th day of December, 1925.

ALBERT S. HOVELU 

